On Mon, Jul 20, 2026 at 05:24:12PM +0100, Fuad Tabba wrote:
> The nVHE hypervisor takes host virtual addresses as hypercall arguments
> and translates each with kern_hyp_va() before use. Nothing marks them as
> host-owned, so dereferencing one untranslated at EL2 - a recurring bug
> class - is invisible to the compiler.
>
> Add a __hostva sparse address space, active only for EL2 code, and tag
> the host-VA parameters in the hypercall declarations. kern_hyp_va_host()
> is the only sanctioned unwrap: it translates the address, preserves the
> pointee type (stripped of qualifiers, as with the percpu accessors) and
> drops the tag with a __force cast, so an untranslated host VA fails
> sparse. The tag flows from the shared declaration into the generated
> handler and on into the donated-memory and tracing-descriptor helpers,
> so a handler cannot extract a host VA without it. Host code sees plain
> pointers, and the tag is checker-only: no code is generated.
>
> Signed-off-by: Fuad Tabba <[email protected]>
> ---
> arch/arm64/include/asm/kvm_hcall.h | 43 ++++++++++++-------
> arch/arm64/include/asm/kvm_mmu.h | 10 +++++
> arch/arm64/kvm/hyp/include/nvhe/pkvm.h | 6 ++-
> arch/arm64/kvm/hyp/include/nvhe/trace.h | 5 ++-
> arch/arm64/kvm/hyp/nvhe/hyp-main.c | 57 +++++++++++++------------
> arch/arm64/kvm/hyp/nvhe/pkvm.c | 11 ++---
> arch/arm64/kvm/hyp/nvhe/trace.c | 4 +-
> 7 files changed, 82 insertions(+), 54 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_hcall.h
> b/arch/arm64/include/asm/kvm_hcall.h
> index 6aa2df90a14a4..3033a6ba1462a 100644
> --- a/arch/arm64/include/asm/kvm_hcall.h
> +++ b/arch/arm64/include/asm/kvm_hcall.h
> @@ -27,6 +27,18 @@ struct kvm_vcpu;
> struct vgic_v3_cpu_if;
> struct vgic_v5_cpu_if;
>
> +/*
> + * A host VA carried by a hypercall argument. At EL2 such a pointer must not
> + * be dereferenced until it is translated with kern_hyp_va_host(); sparse
> + * flags any use that skips the translation. The tag describes the EL2 view
> + * only: the host dereferences its own VAs freely.
> + */
> +#if defined(__KVM_NVHE_HYPERVISOR__) && defined(__CHECKER__)
> +#define __hostva __attribute__((noderef, address_space(__hostva)))
> +#else
> +#define __hostva
> +#endif
Could we have __kern, just like we have __user.
Ideally this could be used later to mark the values we don't trust, so not only
VAs but also nr_pages. In mem_protect.c e.g.
size_t pfn_range_is_valid(u64 __kern pfn, u64 __kern nr_pages)
so that size is only trusted once pfn_range_is_valid() has run.
And beside, that matches "kern_hyp_va"
> +
> /*
> * Hypercall signatures are declared as (type, name) argument pairs.
> * __KVM_HCALL_MAP() applies a macro to each pair, in the mold of __MAP()
> @@ -157,24 +169,24 @@ DECLARE_KVM_HOST_HCALL0(int, __pkvm_prot_finalize)
>
> /* Hypercalls that are always available and common to [nh]VHE/pKVM. */
> DECLARE_KVM_HOST_HCALL_VOID(__kvm_adjust_pc, 1,
> - struct kvm_vcpu *, vcpu)
> + struct kvm_vcpu __hostva *, vcpu)
> DECLARE_KVM_HOST_HCALL(int, __kvm_vcpu_run, 1,
> - struct kvm_vcpu *, vcpu)
> + struct kvm_vcpu __hostva *, vcpu)
> DECLARE_KVM_HOST_HCALL0_VOID(__kvm_flush_vm_context)
> DECLARE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid_ipa, 3,
> - struct kvm_s2_mmu *, mmu, phys_addr_t, ipa, int, level)
> + struct kvm_s2_mmu __hostva *, mmu, phys_addr_t, ipa, int, level)
> DECLARE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid_ipa_nsh, 3,
> - struct kvm_s2_mmu *, mmu, phys_addr_t, ipa, int, level)
> + struct kvm_s2_mmu __hostva *, mmu, phys_addr_t, ipa, int, level)
> DECLARE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid, 1,
> - struct kvm_s2_mmu *, mmu)
> + struct kvm_s2_mmu __hostva *, mmu)
> DECLARE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid_range, 3,
> - struct kvm_s2_mmu *, mmu, phys_addr_t, start, unsigned long, pages)
> + struct kvm_s2_mmu __hostva *, mmu, phys_addr_t, start, unsigned long,
> pages)
> DECLARE_KVM_HOST_HCALL_VOID(__kvm_flush_cpu_context, 1,
> - struct kvm_s2_mmu *, mmu)
> + struct kvm_s2_mmu __hostva *, mmu)
> DECLARE_KVM_HOST_HCALL_VOID(__kvm_timer_set_cntvoff, 1,
> u64, cntvoff)
> DECLARE_KVM_HOST_HCALL(int, __tracing_load, 2,
> - void *, desc_hva, size_t, desc_size)
> + void __hostva *, desc_hva, size_t, desc_size)
> DECLARE_KVM_HOST_HCALL0_VOID(__tracing_unload)
> DECLARE_KVM_HOST_HCALL(int, __tracing_enable, 1,
> bool, enable)
> @@ -189,13 +201,13 @@ DECLARE_KVM_HOST_HCALL(int, __tracing_enable_event, 2,
> DECLARE_KVM_HOST_HCALL_VOID(__tracing_write_event, 1,
> u64, id)
> DECLARE_KVM_HOST_HCALL_VOID(__vgic_v3_save_aprs, 1,
> - struct vgic_v3_cpu_if *, cpu_if)
> + struct vgic_v3_cpu_if __hostva *, cpu_if)
> DECLARE_KVM_HOST_HCALL_VOID(__vgic_v3_restore_vmcr_aprs, 1,
> - struct vgic_v3_cpu_if *, cpu_if)
> + struct vgic_v3_cpu_if __hostva *, cpu_if)
> DECLARE_KVM_HOST_HCALL_VOID(__vgic_v5_save_apr, 1,
> - struct vgic_v5_cpu_if *, cpu_if)
> + struct vgic_v5_cpu_if __hostva *, cpu_if)
> DECLARE_KVM_HOST_HCALL_VOID(__vgic_v5_restore_vmcr_apr, 1,
> - struct vgic_v5_cpu_if *, cpu_if)
> + struct vgic_v5_cpu_if __hostva *, cpu_if)
>
> /* Hypercalls that are available only when pKVM has finalised. */
> DECLARE_KVM_HOST_HCALL(int, __pkvm_host_share_hyp, 1,
> @@ -220,10 +232,11 @@ DECLARE_KVM_HOST_HCALL0(int, __pkvm_reserve_vm)
> DECLARE_KVM_HOST_HCALL_VOID(__pkvm_unreserve_vm, 1,
> pkvm_handle_t, handle)
> DECLARE_KVM_HOST_HCALL(int, __pkvm_init_vm, 3,
> - struct kvm *, host_kvm, void *, vm_hva, void *, pgd_hva)
> + struct kvm __hostva *, host_kvm, void __hostva *, vm_hva,
> + void __hostva *, pgd_hva)
> DECLARE_KVM_HOST_HCALL(int, __pkvm_init_vcpu, 3,
> - pkvm_handle_t, handle, struct kvm_vcpu *, host_vcpu,
> - void *, vcpu_hva)
> + pkvm_handle_t, handle, struct kvm_vcpu __hostva *, host_vcpu,
> + void __hostva *, vcpu_hva)
> DECLARE_KVM_HOST_HCALL0(int, __pkvm_vcpu_in_poison_fault)
> DECLARE_KVM_HOST_HCALL(int, __pkvm_force_reclaim_guest_page, 1,
> phys_addr_t, phys)
> diff --git a/arch/arm64/include/asm/kvm_mmu.h
> b/arch/arm64/include/asm/kvm_mmu.h
> index 6eae7e7e2a684..55fac40377c03 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -7,6 +7,8 @@
> #ifndef __ARM64_KVM_MMU_H__
> #define __ARM64_KVM_MMU_H__
>
> +#include <linux/compiler.h>
> +
> #include <asm/page.h>
> #include <asm/memory.h>
> #include <asm/mmu.h>
> @@ -140,6 +142,14 @@ static __always_inline unsigned long
> __kern_hyp_va(unsigned long v)
>
> #define kern_hyp_va(v) ((typeof(v))(__kern_hyp_va((unsigned long)(v))))
>
> +/*
> + * Translate a __hostva-tagged host VA, dropping the tag: the only sanctioned
> + * unwrap. Translation only, no ownership or bounds validation; the result
> + * carries the pointee type stripped of the tag and of any cv-qualifiers.
> + */
> +#define kern_hyp_va_host(v) \
> + ((TYPEOF_UNQUAL(*(v)) *)__kern_hyp_va((unsigned long)(__force void
> *)(v)))
> +
> extern u32 __hyp_va_bits;
>
> /*
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
> b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
> index 2643a1a819668..dcbe8b8913270 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
> @@ -7,6 +7,7 @@
> #ifndef __ARM64_KVM_NVHE_PKVM_H__
> #define __ARM64_KVM_NVHE_PKVM_H__
>
> +#include <asm/kvm_hcall.h>
> #include <asm/kvm_pkvm.h>
>
> #include <nvhe/gfp.h>
> @@ -69,9 +70,10 @@ void pkvm_hyp_vm_table_init(void *tbl);
>
> int __pkvm_reserve_vm(void);
> void __pkvm_unreserve_vm(pkvm_handle_t handle);
> -int __pkvm_init_vm(struct kvm *host_kvm, void *vm_hva, void *pgd_hva);
> +int __pkvm_init_vm(struct kvm *host_kvm, void __hostva *vm_hva,
> + void __hostva *pgd_hva);
> int __pkvm_init_vcpu(pkvm_handle_t handle, struct kvm_vcpu *host_vcpu,
> - void *vcpu_hva);
> + void __hostva *vcpu_hva);
>
> int __pkvm_reclaim_dying_guest_page(pkvm_handle_t handle, u64 gfn);
> int __pkvm_start_teardown_vm(pkvm_handle_t handle);
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/trace.h
> b/arch/arm64/kvm/hyp/include/nvhe/trace.h
> index 4aa36fd76b9e2..58e0ad3329034 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/trace.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/trace.h
> @@ -4,6 +4,7 @@
>
> #include <linux/trace_remote_event.h>
>
> +#include <asm/kvm_hcall.h>
> #include <asm/kvm_hyptrace.h>
>
> static inline pid_t __tracing_get_vcpu_pid(struct kvm_cpu_context *host_ctxt)
> @@ -46,7 +47,7 @@ static inline pid_t __tracing_get_vcpu_pid(struct
> kvm_cpu_context *host_ctxt)
> void *tracing_reserve_entry(unsigned long length);
> void tracing_commit_entry(void);
>
> -int __tracing_load(void *desc_va, size_t desc_size);
> +int __tracing_load(void __hostva *desc_va, size_t desc_size);
> void __tracing_unload(void);
> int __tracing_enable(bool enable);
> int __tracing_swap_reader(unsigned int cpu);
> @@ -59,7 +60,7 @@ static inline void tracing_commit_entry(void) { }
> #define HYP_EVENT(__name, __proto, __struct, __assign, __printk) \
> static inline void trace_##__name(__proto) {}
>
> -static inline int __tracing_load(void *desc_va, size_t desc_size) { return
> -ENODEV; }
> +static inline int __tracing_load(void __hostva *desc_va, size_t desc_size) {
> return -ENODEV; }
> static inline void __tracing_unload(void) { }
> static inline int __tracing_enable(bool enable) { return -ENODEV; }
> static inline int __tracing_swap_reader(unsigned int cpu) { return -ENODEV; }
> diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> index f2501249f4391..679b6df9c998d 100644
> --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> @@ -269,7 +269,7 @@ DEFINE_KVM_HOST_HCALL0_VOID(__pkvm_vcpu_put)
> }
>
> DEFINE_KVM_HOST_HCALL(int, __kvm_vcpu_run, 1,
> - struct kvm_vcpu *, host_vcpu)
> + struct kvm_vcpu __hostva *, host_vcpu)
> {
> int ret;
>
> @@ -294,7 +294,7 @@ DEFINE_KVM_HOST_HCALL(int, __kvm_vcpu_run, 1,
>
> sync_hyp_vcpu(hyp_vcpu);
> } else {
> - struct kvm_vcpu *vcpu = kern_hyp_va(host_vcpu);
> + struct kvm_vcpu *vcpu = kern_hyp_va_host(host_vcpu);
>
> /* The host is fully trusted, run its vCPU directly. */
> fpsimd_lazy_switch_to_guest(vcpu);
> @@ -421,9 +421,9 @@ DEFINE_KVM_HOST_HCALL(int, __pkvm_host_mkyoung_guest, 1,
> }
>
> DEFINE_KVM_HOST_HCALL_VOID(__kvm_adjust_pc, 1,
> - struct kvm_vcpu *, vcpu)
> + struct kvm_vcpu __hostva *, vcpu)
> {
> - __kvm_adjust_pc(kern_hyp_va(vcpu));
> + __kvm_adjust_pc(kern_hyp_va_host(vcpu));
> }
>
> DEFINE_KVM_HOST_HCALL0_VOID(__kvm_flush_vm_context)
> @@ -432,27 +432,27 @@ DEFINE_KVM_HOST_HCALL0_VOID(__kvm_flush_vm_context)
> }
>
> DEFINE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid_ipa, 3,
> - struct kvm_s2_mmu *, mmu, phys_addr_t, ipa, int, level)
> + struct kvm_s2_mmu __hostva *, mmu, phys_addr_t, ipa, int, level)
> {
> - __kvm_tlb_flush_vmid_ipa(kern_hyp_va(mmu), ipa, level);
> + __kvm_tlb_flush_vmid_ipa(kern_hyp_va_host(mmu), ipa, level);
> }
>
> DEFINE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid_ipa_nsh, 3,
> - struct kvm_s2_mmu *, mmu, phys_addr_t, ipa, int, level)
> + struct kvm_s2_mmu __hostva *, mmu, phys_addr_t, ipa, int, level)
> {
> - __kvm_tlb_flush_vmid_ipa_nsh(kern_hyp_va(mmu), ipa, level);
> + __kvm_tlb_flush_vmid_ipa_nsh(kern_hyp_va_host(mmu), ipa, level);
> }
>
> DEFINE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid_range, 3,
> - struct kvm_s2_mmu *, mmu, phys_addr_t, start, unsigned long, pages)
> + struct kvm_s2_mmu __hostva *, mmu, phys_addr_t, start, unsigned long,
> pages)
> {
> - __kvm_tlb_flush_vmid_range(kern_hyp_va(mmu), start, pages);
> + __kvm_tlb_flush_vmid_range(kern_hyp_va_host(mmu), start, pages);
> }
>
> DEFINE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid, 1,
> - struct kvm_s2_mmu *, mmu)
> + struct kvm_s2_mmu __hostva *, mmu)
> {
> - __kvm_tlb_flush_vmid(kern_hyp_va(mmu));
> + __kvm_tlb_flush_vmid(kern_hyp_va_host(mmu));
> }
>
> DEFINE_KVM_HOST_HCALL_VOID(__pkvm_tlb_flush_vmid, 1,
> @@ -468,9 +468,9 @@ DEFINE_KVM_HOST_HCALL_VOID(__pkvm_tlb_flush_vmid, 1,
> }
>
> DEFINE_KVM_HOST_HCALL_VOID(__kvm_flush_cpu_context, 1,
> - struct kvm_s2_mmu *, mmu)
> + struct kvm_s2_mmu __hostva *, mmu)
> {
> - __kvm_flush_cpu_context(kern_hyp_va(mmu));
> + __kvm_flush_cpu_context(kern_hyp_va_host(mmu));
> }
>
> DEFINE_KVM_HOST_HCALL_VOID(__kvm_timer_set_cntvoff, 1,
> @@ -499,15 +499,15 @@ DEFINE_KVM_HOST_HCALL0_VOID(__vgic_v3_init_lrs)
> }
>
> DEFINE_KVM_HOST_HCALL_VOID(__vgic_v3_save_aprs, 1,
> - struct vgic_v3_cpu_if *, cpu_if)
> + struct vgic_v3_cpu_if __hostva *, cpu_if)
> {
> - __vgic_v3_save_aprs(kern_hyp_va(cpu_if));
> + __vgic_v3_save_aprs(kern_hyp_va_host(cpu_if));
> }
>
> DEFINE_KVM_HOST_HCALL_VOID(__vgic_v3_restore_vmcr_aprs, 1,
> - struct vgic_v3_cpu_if *, cpu_if)
> + struct vgic_v3_cpu_if __hostva *, cpu_if)
> {
> - __vgic_v3_restore_vmcr_aprs(kern_hyp_va(cpu_if));
> + __vgic_v3_restore_vmcr_aprs(kern_hyp_va_host(cpu_if));
> }
>
> DEFINE_KVM_HOST_HCALL(int, __pkvm_init, 4,
> @@ -579,16 +579,17 @@ DEFINE_KVM_HOST_HCALL_VOID(__pkvm_unreserve_vm, 1,
> }
>
> DEFINE_KVM_HOST_HCALL(int, __pkvm_init_vm, 3,
> - struct kvm *, host_kvm, void *, vm_hva, void *, pgd_hva)
> + struct kvm __hostva *, host_kvm, void __hostva *, vm_hva,
> + void __hostva *, pgd_hva)
> {
> - return __pkvm_init_vm(kern_hyp_va(host_kvm), vm_hva, pgd_hva);
> + return __pkvm_init_vm(kern_hyp_va_host(host_kvm), vm_hva, pgd_hva);
> }
>
> DEFINE_KVM_HOST_HCALL(int, __pkvm_init_vcpu, 3,
> - pkvm_handle_t, handle, struct kvm_vcpu *, host_vcpu,
> - void *, vcpu_hva)
> + pkvm_handle_t, handle, struct kvm_vcpu __hostva *, host_vcpu,
> + void __hostva *, vcpu_hva)
> {
> - return __pkvm_init_vcpu(handle, kern_hyp_va(host_vcpu), vcpu_hva);
> + return __pkvm_init_vcpu(handle, kern_hyp_va_host(host_vcpu), vcpu_hva);
> }
>
> DEFINE_KVM_HOST_HCALL0(int, __pkvm_vcpu_in_poison_fault)
> @@ -623,7 +624,7 @@ DEFINE_KVM_HOST_HCALL(int, __pkvm_finalize_teardown_vm, 1,
> }
>
> DEFINE_KVM_HOST_HCALL(int, __tracing_load, 2,
> - void *, desc_hva, size_t, desc_size)
> + void __hostva *, desc_hva, size_t, desc_size)
> {
> return __tracing_load(desc_hva, desc_size);
> }
> @@ -670,15 +671,15 @@ DEFINE_KVM_HOST_HCALL_VOID(__tracing_write_event, 1,
> }
>
> DEFINE_KVM_HOST_HCALL_VOID(__vgic_v5_save_apr, 1,
> - struct vgic_v5_cpu_if *, cpu_if)
> + struct vgic_v5_cpu_if __hostva *, cpu_if)
> {
> - __vgic_v5_save_apr(kern_hyp_va(cpu_if));
> + __vgic_v5_save_apr(kern_hyp_va_host(cpu_if));
> }
>
> DEFINE_KVM_HOST_HCALL_VOID(__vgic_v5_restore_vmcr_apr, 1,
> - struct vgic_v5_cpu_if *, cpu_if)
> + struct vgic_v5_cpu_if __hostva *, cpu_if)
> {
> - __vgic_v5_restore_vmcr_apr(kern_hyp_va(cpu_if));
> + __vgic_v5_restore_vmcr_apr(kern_hyp_va_host(cpu_if));
> }
>
> typedef void (*hcall_t)(struct kvm_cpu_context *);
> diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c
> index 205c52535c887..bfc9f07f336a1 100644
> --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c
> +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c
> @@ -644,9 +644,9 @@ static size_t pkvm_get_hyp_vm_size(unsigned int nr_vcpus)
> size_mul(sizeof(struct pkvm_hyp_vcpu *), nr_vcpus));
> }
>
> -static void *map_donated_memory_noclear(void *host_va, size_t size)
> +static void *map_donated_memory_noclear(void __hostva *host_va, size_t size)
> {
> - void *va = kern_hyp_va(host_va);
> + void *va = kern_hyp_va_host(host_va);
>
> if (!PAGE_ALIGNED(va))
> return NULL;
> @@ -658,7 +658,7 @@ static void *map_donated_memory_noclear(void *host_va,
> size_t size)
> return va;
> }
>
> -static void *map_donated_memory(void *host_va, size_t size)
> +static void *map_donated_memory(void __hostva *host_va, size_t size)
> {
> void *va = map_donated_memory_noclear(host_va, size);
>
> @@ -805,7 +805,8 @@ void teardown_selftest_vm(void)
> *
> * Return 0 success, negative error code on failure.
> */
> -int __pkvm_init_vm(struct kvm *host_kvm, void *vm_hva, void *pgd_hva)
> +int __pkvm_init_vm(struct kvm *host_kvm, void __hostva *vm_hva,
> + void __hostva *pgd_hva)
> {
> struct pkvm_hyp_vm *hyp_vm = NULL;
> size_t vm_size, pgd_size;
> @@ -896,7 +897,7 @@ static int register_hyp_vcpu(struct pkvm_hyp_vm *hyp_vm,
> }
>
> int __pkvm_init_vcpu(pkvm_handle_t handle, struct kvm_vcpu *host_vcpu,
> - void *vcpu_hva)
> + void __hostva *vcpu_hva)
> {
> struct pkvm_hyp_vcpu *hyp_vcpu;
> struct pkvm_hyp_vm *hyp_vm;
> diff --git a/arch/arm64/kvm/hyp/nvhe/trace.c b/arch/arm64/kvm/hyp/nvhe/trace.c
> index 97203ddd3cf45..5d0fcdce9507d 100644
> --- a/arch/arm64/kvm/hyp/nvhe/trace.c
> +++ b/arch/arm64/kvm/hyp/nvhe/trace.c
> @@ -206,9 +206,9 @@ static bool hyp_trace_desc_is_valid(struct hyp_trace_desc
> *desc, size_t desc_siz
> return true;
> }
>
> -int __tracing_load(void *desc_hva, size_t desc_size)
> +int __tracing_load(void __hostva *desc_hva, size_t desc_size)
> {
> - struct hyp_trace_desc *desc = kern_hyp_va(desc_hva);
> + struct hyp_trace_desc *desc = kern_hyp_va_host(desc_hva);
> int ret;
>
> ret = __admit_host_mem(desc, desc_size);
> --
> 2.39.5
>
--
Vincent
